The invention is in the field of electronic reproduction technology and is directed to a light beam deflection unit in a scanner device for an originals scanning apparatus or recording apparatus. Such a scanner device essentially comprises a light source, for example a laser light source, that generates a light beam that is periodically deflected across a subject with the rotating light beam deflection unit.
In an originals scanning apparatus, also referred to as input scanner, a light beam generated in a scanner device is conducted pixel-by-pixel and line-by-line over an original to be scanned, and the scan light the original reflects or allows to pass is converted into an image signal by an optoelectronic transducer. In a recording apparatus, also referred to as a recorder, exposer or output scanner, the light beam acquired in a scanner device is modulated in intensity by an image signal for recording information and is conducted pixel-by-pixel and line-by-line across a light-sensitive recording material.
In the case of a flat bed scanner, the holder for the original or, the recording material is a plane surface over which the light beam is conducted pixel-by-pixel and line-by-line, and which moves relative to the scanner device. In the case of an inside drum apparatus, the holder for the original or, for the recording medium is designed as a stationary half-shell or trough. The scanner device moves parallel to the longitudinal axis of the holder, and the light beam is radially conducted over the original or, the recording material perpendicular to the longitudinal axis.
An inside drum apparatus is disclosed, for example, by EP-A-0 354 028. The light beam deflection unit therein is designed as a reflective surface arranged transversely relative to the direction of light propagation and is connected to a rotating shaft. The light beam is conducted onto a recording material with the assistance of the reflective surface.
Contaminants can collect at the reflective surface during operation of the recording apparatus, and air turbulence can arise at high speeds due to the asymmetrical design with respect to the axis of rotation. This air turbulence leads to noise loads, causes additional dirt in the region of the reflective surface and deteriorates the uniform rotation of the reflective surface.
DE-A41 24 229 already discloses a light beam deflection means with a light entry face and a light exit face for the perpendicularly deflected light beam that is composed of a rotationally seated carrier prism and of a light-transmissive deflection prism that extends in the direction of its rotational axis. The surface of the deflection prism adjoining the carrier prism is designed as a reflection face that proceeds transversely relative to the rotational axis. The deflection prism is glued to the carrier prism, and the two prisms supplement each other at least in regions to form a unit that is symmetrical relative to the rotational axis. Disk-shaped cover elements that project beyond the unit in radial expanse are arranged to the side of the unit.
Only slight air turbulence, contamination and unquiet running in fact occur in this light beam deflection unit due to the cover elements; the manufacture thereof, however, is comparatively complicated since the cover elements must be precisely manufactured and precisely centered at the unit.
DE-A41 30 977 discloses another light beam deflection unit that is composed of a transparent body designed as a spherical segment that has a light entry face, a reflection face, and a light exit face, and is further composed of a carrier member likewise designed as a spherical segment that is glued to the transparent body at the reflection face. The unit formed of the transparent body and of carrier member is rotatable around an axis residing vertically relative to the light entry face and has an outside contour that is rotational-symmetrical at least with reference to the axis. As a result of the spherical designing of the light beam deflection unit, this can rotate at a relatively high speed without creating significant air turbulence and bearing noise.
The known light beam deflection units have proven themselves well up to now. However, light sources, preferably laser light sources, with higher luminous power are required for exposing certain recording materials. In practice, the required luminous powers can currently only be generated by light sources that generate light with a greater wavelength of, for example, 1064 nm. In order to deflect a light beam having a greater wavelength, the light beam deflection units must have a correspondingly large entry aperture in order to obtain comparable pixel sizes and line widths in the exposure, despite the greater wavelength.
The enlargement of the entry aperture in a light beam deflection unit, however, results in an increase in the running noises and in unquiet running. A further disadvantage is that the air turbulences contaminate the reflective surfaces of the light beam deflection unit, this leading to optical losses and, thus, poorer reproduction quality.